Manufacturing a semiconductor integrated circuit (IC) typically involves numerous processing techniques that require elevated wafer temperatures to perform the desired processes, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), dry etching, or other processing techniques. As a known wafer holding apparatus, an electrostatic chuck including a heating element is commonly employed to support a semiconductor wafer in a stationary position and transfer heat generated from the heating element to the wafer during the various processes.
FIG. 1 illustrates a prior art dipole-type electrostatic chuck 10 utilized as a wafer supporting and heating apparatus. Electrostatic chuck 10 comprises either a pair of or plural pairs of electrodes 12 embedded in a wafer supporting stage, which typically comprises a mounting surface 15 made of heat conducting dielectrics, such as a heat conducting ceramic. When an alternating voltage is applied between the electrodes 12, a reverse polarity charge is typically induced in wafer substrate 18. Wafer substrate 18 is thus electrostatically attracted to the supporting stage utilizing the force generated between the wafer substrate and the electrodes. A heating circuit is also used to supply electricity to the supporting stage to heat the mounting surface 15 of the electrostatic chuck 10. Heat transfer then occurs between mounting surface 15 and wafer substrate 18 held thereon so that wafer substrate 18 reaches a desired temperature range suitable for processing the wafer.
Conventional electrostatic chucks, however, have the following problems. First, during a wafer fabrication process, such as a CVD or impurity doping process, a semiconductor wafer may be subjected to an elevated temperature on the order of 800° C. or higher. The wafer processed within such a high temperature range may be under significant heat stress, which typically causes wafer bowing or warping as illustrated in FIG. 1. This problem causes the wafer substrate 18 to lose direct abutting contact with the mounting surface 15 where the bowing or warping occurs. A considerable portion of the heat generated by mounting surface 15 would be transferred to the wafer spots that contact mounting surface 15, but not to the bowed or warped portions of wafer substrate 18. This causes further temperature non-uniformity in wafer substrate 18.
Additionally, for the system where alternating voltage is applied to the electrodes 12, electric charge is accumulated in the back surface of wafer substrate 18 while the wafer is being attracted, and the accumulated charge makes the separation of the substrate from the chuck difficult. Moreover, although an electrostatic chuck operated through an alternating voltage exerts an attractive force to the wafer substrate held thereon, the attractive force is typically not adapted to the mechanical stress created by the uneven heat distribution in a wafer substrate. As a result, when the mechanical stress accumulated in a wafer substrate exceeds a critical point, the wafer substrate may crack or even break.
Furthermore, the trend of increasing wafer diameter in semiconductor manufacturing continues as part of the effort to increase the throughput of a semiconductor fabrication facility and offset the high cost imposed by the processing equipment in advanced processing technology. The uneven heat distribution as described above may create increased mechanical stress in a wafer substrate of increased dimension, causing more severe bowing or warping effects.